1. Field of the Invention
The present invention relates to the field of zipper slides, and more particularly to a zipper slide provided with means for restraining interlocking teeth thereof from disengaging when the slide has been moved with a coupled pull tab to a desired position on a zipper. The teeth on the zipper tape may be made from either metal or plastic materials.
2. Description of the Prior Art
FIG. 1 to FIG. 3 illustrate a typical needle locking mechanism for a zipper slide. As shown in FIG. 1, the needle locking mechanism generally includes a slide body 10 that is integrally made by metal or the like, a leaf spring piece 11, and a pull tab unit 12. On a top surface of the slide body 10 there are provided a first joint portion 101 and a second joint portion 102. The first joint portion 101 and the second joint portion 102 are used to buckle the leaf spring piece 11 and also the pull tab unit 12 in place. Engagement channel 104 is provided in a front end of the slide body 10. As shown in FIG. 2, the engagement channel 104 slides along the lengths of interlocking teeth 15 of the teeth tapes 13 and 14 to facilitate the engagement and disengagement thereof.
The leaf spring piece 11 buckles the pull tab unit 12 by passing through opening 121 of the pull tab unit 12. As illustrated, the leaf spring piece 11 has a hooked portion 111 in one end and a downwardly extending portion 112 formed in the other end. When assembling, the hooked portion 111 is inserted into the front end of the slide body 10, as shown in FIG. 2. The first joint portion 101 is then bent down so as to clip and fasten the leaf spring piece 11. The extending portion 112 is inserted into a slot 103 located on the rear of the slide body 10.
Still referring to FIG. 2, the pull tab unit 12 facilitates manipulation of sliding the slide body to engage or disengage the metal teeth 15 of opposite teeth tapes 13 and 14. The opening 121 is formed on the pull tab unit 12 and is designed to allow the passing of the leaf spring piece 11. One side of the opening 121 is a beam 123 with a recess portion 122 thereon. The beam 123 is coupled with the second joint portion 102 and is restrained by the leaf spring piece 11. The recess portion 122 is provided for positioning purpose for the leaf spring piece 11. Typically, the width of the recess portion 122 is substantially equivalent to the width of the leaf spring piece 11.
The horizontal level of the first joint portion 101 is lower than the level of the second joint portion 102. As shown in FIG. 3, when the pull tab unit 12 is pulled in an angle relative to the slide body 10, the beam 123 slightly rotates and the extending portion 112 of the leaf spring piece 11 is uplifted by the recess portion 122 to leave the slot 103. By this way, the slide body can smoothly slides along the two lengths of interlocking teeth to facilitate the engagement and disengagement. When one stop pulling the pull tab unit 12 the extending portion 112 is pushed back into the slot 103 to lock the teeth in place and thus preventing slipping of the slide body 10 and unwarily open of the zipper.
However, the above-mentioned prior art structure is only suited for metal teeth 15 that have smaller inter-space between two adjacent teeth. When the prior art structure is applied to two lengths of plastic teeth the extending portion 112 of the leaf spring piece usually malfunctions due to a larger inter-space between two adjacent teeth. As shown in FIG. 3, the extending portion 112 of the leaf spring piece 11 is too close to the front of the engagement line 131 at one side of the teeth tape 13. This deteriorates the functioning of the extending portion 112 to prevent slide body 10 from sliding down along the lengths of interlocking teeth. Consequently, there is a strong need to provide an improved needle locking mechanism for zipper slides.
Accordingly, it is a primary object of the present invention to provide an improved needle locking mechanism for zipper slides. The needle locking mechanism according to this invention is capable of engaging with either metal teeth or plastic teeth in a more tight-knit way.
According to the claimed invention, a needle locking structure of a zipper slide for engaging or disengaging two lengths of teeth on two opposite teeth tapes is provided. A monolithic main body has two joint portions formed thereon. An engagement part is formed on each side of the main body. A spring piece is fixed by the joint portions of the main body. A pull tab unit is fixed by the joint portions of the main body for facilitating the manipulation of pulling the zipper slide. A laterally shifted extending portion is provided at one end of the spring piece. Since the extension portion jabs the top of an engagement line of one of the teeth tapes, the friction force is increased whereby improving the positioning of the main body and preventing unwarily sliding of the zipper slide.